Hal,
I don't do that much Voice/Data work so for me the cost difference doesn't amount to much. I find it easier to just stock one type of cable that I can use for both voice and data. Cat5 cable is good for both and I only have to worry about carrying one type on my service truck. I used to carry both on my truck and used Cat3 for voice and Cat5 for computer networks but decided it was easier to stock just one. Saves space.
Does it really bother you that much when someone uses Cat5 for voice. [Linked Image]